Precast concrete members have become commonly used in the construction of walls and decks. These members are manufactured in a facility and then shipped to the job location and erected. The typical prefabricated concrete members used in parking lots to form the deck are in the form of beams. The horizontal portion of the beam is a slab which is the load bearing surface and generally contains reinforcing mesh or pre-stressed strands. To form the deck, the concrete members are positioned adjacent to each other so that the edges of the slabs are abutting.
When using concrete beams to form a deck or wall, it is possible for the members to move relative to each other. This is the result of wind forces or thermal expansion. In order to prevent or minimize the relative movement and to further increase the strength of the structure, metal inserts called "weldments" are placed in the edges of the slab. When the concrete slabs are positioned for final assembly, the metal pieces of one slab are aligned with and opposite to a complementary metal piece in the adjacent slab. The metal pieces are welded together to provide a unitary structure which is much stronger than had the slabs not been joined.
One type of weldment which was commonly used in the past was a "U" shaped cylindrical reinforcing bar. Such bars were commonly used in the precast concrete slabs. The reinforcing bars were bent in a generally "U" shaped configuration with the arms embedded in the concrete and the base portion of the "U" shaped configuration exposed along the edge of the concrete slab. This exposed portion was the portion which was welded to a reinforcing bar embedded in an adjacent concrete slab. A problem with this type of weldment is that the parallel arms of the "U" shaped bar cannot be precisely positioned within the concrete slab as it is formed. Once the concrete is poured into the mold, it is impossible to determine the location of the "U" shaped parallel portions of the bar within the slab. Due to this, the reinforcing bar weldments are often not properly positioned within the slab and will pull out of the slab under load.
An improvement of the reinforcing bar weldment is illustrated in U.S. Pat. No. 3,958,954 entitled Concrete Weldment. The problem with the weldment illustrated in the '954 patent is that the tails 26 which are embedded in the concrete are disposed at an angle with respect to the vertical axis. In order for the reinforcing mesh to rest upon these tails, the tails must either be turned at a downward angle into the concrete or be placed further down into the slab to allow the mesh to be buried at least one and one half inches below the top surface of the concrete slab. Ideally, the reinforcing mesh should come within one inch of the edge of the slab. Thus, the design illustrated in the '954 patent does not permit the mesh to come within one inch of the edge and still be buried one and a half inches below the top surface of the concrete without giving rise to the problems as discussed above. If the tails are angled downward, there is a great possibility that the tails could come very close to, if not protrude through the bottom of the slab. Another problem in the '954 embodiment is that the method of manufacturing the slab does not provide that the central portion 22 of the weldment 20 will remain free of concrete during manufacture. This either decreases the weldable surface or results in concrete cracks and spalling from the welding operation.
Accordingly, it is an object of the present invention to provide a new and improved concrete weldment which is inserted and cast into the edge of a concrete slab. It is a further object to provide a weldment which reduces the possibility of concrete cracks and spalling from the welding operation.
It is another object to provide a weldment which will support a reinforcing mesh within the concrete mold during the molding operation. Related to this object is the object of providing a weldment which will accurately position the mesh within the mold and retain it in this position such that the resulting slab has the mesh buried in the slab at a proper depth and within a predetermined distance from the edge of the slab.
It is yet another object to provide a weldment having arms which extend into the concrete slab to secure the weldment into the slab, yet, not have the arms protrude through the bottom of the slab.
Another object is the object of providing a weldment which has a weldable portion which is free from concrete both in the welding area and along its top edge. The advantage of this design is that it increases the weldable area and allows for thermal expansion of the weldment without cracking and spalling of the concrete.
Yet, another object is the object of providing a method of manufacturing concrete slabs such that the weldment is cast into the slab yet concrete is restricted from flowing over the front of the weldable surface of the weldment or over the top edge of the front portion of the weldment. A related object is to provide a mold blockout which protects the weldment during the formation of the concrete slab yet is removable and reusable in the manufacture of subsequent concrete slabs.
Applicant's invention solves the problems set forth above. Applicant provides a weldment which is embedded into the concrete slab structure in the fabrication process. The weldment has a central plate which forms the weldable surface of the weldment. It is perpendicularly positioned with respect to the horizontal plane of the concrete slab. This is accomplished by accurately positioning the weldment with respect to the mold cavity. The planar surface of the central plate is positioned along an edge of the concrete slab. There are a pair of outstanding arms extending divergingly outward from each of the ends of the central plate. The outstanding arms remain at a constant height across their length with the height of the arms being selected to support the reinforcing mesh at a predetermined depth within the concrete slab. The weldment is accurately positioned within the mold by means of a positioning screw which passes through a portion of the mold and into the weldment. Thus, the weldment is accurately positioned each and every time within the mold before the concrete is poured. A blockout is placed on top of the top edge of the central plate of the weldment during the manufacturing process. The blockout keeps the concrete from being poured onto the top edge of the central plate and also keeps the outer face of the central plate clear of concrete. After the concrete slab is formed, the blockout is removed leaving the top edge and front surface of the central plate clean. This results in an outer face with an increase in the weldable area and, furthermore, allows for thermal expansion of the weldment without cracking and spalling of the concrete.